Intent to Deprecate and Remove: SVGElement.xmlbase/xmlspace/xmllang

[Philip Jägenstedt]

Primary eng (and PM) emails

phi...@opera.com

Summary

Remove the SVGElement.xmlbase/xmlspace/xmllang IDL attributes, which reflect the xml:base, xml:space and xml:lang content attributes.

Motivation

These have been removed from the SVG spec:

https://github.com/w3c/svgwg/commit/b8f12424b25d5bc132460738e0a1ed9626b4a4a8

https://svgwg.org/svg2-draft/single-page.html#types-InterfaceSVGElement

My main reason for poking at this is xml:base, which Anne (DOM spec editor) wants to get rid of. It looks very ripe for deprecation and removal once its use as a reflected IDL attribute is gone. See https://code.google.com/p/chromium/issues/detail?id=341854

Compatibility Risk

These IDL attributes were added to WebKit in 2005 and 2006:

https://trac.webkit.org/changeset/10577

https://trac.webkit.org/changeset/16337

Gecko doesn't have xmlbase or xmllang, but does have SVGStyleElement.xmlspace with the comment "Spec claims this should be on SVGElement" (which is no longer true).

IE11 has all three attributes.

Alternative implementation suggestion for web developers

Use getAttributeNS and setAttributeNS. However, xml:base may be going away, so use <base href=""> instead if at all possible.

Usage information from UseCounter

https://www.chromestatus.com/metrics/feature/timeline/popularity/681

https://www.chromestatus.com/metrics/feature/timeline/popularity/682

https://www.chromestatus.com/metrics/feature/timeline/popularity/683

These reached stable with M42, but are still rounding to 0%, i.e. virtually unused.

Entry on chromestatus.com, crbug.com, or MDN

https://code.google.com/p/chromium/issues/detail?id=485676

Requesting approval to remove too?

Yes. The low usage makes removal likely safe, and a deprecation message has a very low chance of being seen for the same reason.

[Philip Rogers]

LGTM, this will also let us clean up some cruft in the code (XMLNames.h, special handling in v8, etc).

[Philip Jägenstedt]

To clarify, XMLNames.h will be left after this removal, as all three
attributes are still used internally. If the xml:base removal (next
step) works out, that would remove base from xmlattrs.in. I have no
plans to mess with xml:lang or xml:space, but I have added use
counters for xml:space in case we want to:
https://www.chromestatus.com/metrics/feature/timeline/popularity/679
https://www.chromestatus.com/metrics/feature/timeline/popularity/680

A slight simplifications of the bindings generator should be possible
though, see https://codereview.chromium.org/1137593002/ where Hyunjune
has started working on this.

Philip

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[Chris Harrelson]

LGTM

[Dimitri Glazkov]

LGTM2.

[Jochen Eisinger]

lgtm3